Thanks to whoever shared that tip about Patchy doing laundry! One of my families that need assistance with laundry (because they only have a washtub, which takes forever and doesn't even get the clothes really clean most of the time) actually has a Patchy in the garden, but I had no idea he could be used that way. Guess it's time to befriend him already!
What irritates me about laundry is that if you have more than one hamper and tell a sim to take care of one, they will completely ignore all the others. Even if you queue up several hamper interactions, they will take each set of laundry to the washing machine individually before walking to the next hamper. Depending on the size of your house, this can take all day, and it's even more annoying with washtubs because sims start washing automatically as soon as they get there. The only solution I've found is to let them take the clothes out, then cancel the action so they put them on the floor, and when there's only one filled hamper left, let them do their thing because they will at least pick up any piles of clothes they come across.